The two big differences are the tri bar arrangement and the bottom bracket height. The Trek's armrests fit on top of the tri bar extensions, which themselves sit on top of the base bar. While you can turn the tri bar brackets upside down to run the extensions underneath the base bar, the armrests then won't fit properly because the base bar is in the way. If this were my bike, I would immediately ditch these Bontrager tri bars and fit some with lower armrests. Easton Aeroforce bars would do it – they're about £90 – and there are plenty of others.